To obtain an optimum operation which should be performed currently when information about the front direction of a vehicle such as the position of an obstacle and road width is an important art which leads to next generation safety system and automatic driving. However, because tire force has a non-linear saturation characteristic, it is not easy to obtain a tire force (optimum control strategy) which achieves optimum traveling trajectory in a certain time interval.
Conventionally, a control device which computes a degree of risk based on TIC (time to collision) and controls the vehicle based on the degree of risk has been known (patent document 1). Further, another control device which controls the vehicle based on a distance between an obstacle and the vehicle and a necessary deceleration distance has been known (patent document 2).
Further, it has been known to obtain an optimum control strategy using a dynamic programming (DP) or mathematical programming method for a shortest avoidance problem to a simple mass system.
Further, a method of computing an optimum control strategy corresponding to a vehicle speed and an avoidance distance at the time of starting the avoiding operation by extracting features of the optimum control strategy obtained by online computation by feed forward way has been known.    Patent document 1: Japanese Patent Application Laid-Open No. 2003-32018    Patent document 2: Japanese Patent Application Laid-Open No. 2002-274344